Mora timing organization in producing contrastive geminate/single consonants and long/short vowels by native and non-native speakers of Japanese: effects of speaking rate

The mora timing organization for producing contrastive geminate/single consonants and long/short vowels is a difficult task for non-native speakers of Japanese. This paper investigates characteristics of the segment durations involved in the production of contrastive phonemes by native Japanese speakers and Chinese-speaking subjects, when the speaking rate is changed. From the statistical regression analysis of the measured segment durations of the utterances for a wide range of speaking rates, it was found that: 1) Native Japanese speakers exhibited a clear linear relationship between the segment duration and the average mora duration with few standard errors and individualities, whereas for Chinese-speaking subjects there were large standard errors and individualities though they maneuvered the timing skillfully at a regular speaking rate, 2) it was difficult for Chinese speakers to control the timing when the speaking rate varied, and 3) the normalized standard error in the regression model was a good index of the degree of achievement of the contrastive mora timing organization.